nope,
unsealed - Just like a stock headset, but threadless.
sealed - Headset with sealed bearings, this is a sealed bearing:
Sealed bearing means: its SEALED, so there is no way dirt is coming inside where the bearingballs are. With a stock headset its always the problem that there's dirt in there. With a BMX unsealed headset its less likely but still there will get dirt in the bearings. With a sealed headset its impossible to get dirt IN your bearings. So they always run smooth, if installed right.